This invention relates to medication delivery instruments and, more particularly, to medication delivery pens, such as those used in administering insulin.
Various medication delivery pen designs are known in the prior art, including that shown in U.S. Pat. No. 6,248,095, which issued on Jun. 19, 2001, to one of the inventors herein and the assignee hereto. To administer a dose of medication, such as insulin, using the pen of U.S. Pat. No. 6,248,095, and as is commonly done with other medication delivery pen designs, a dose knob is manually rotated until a desired dose amount is set. Thereafter, a needle cannula is inserted into a patient and a button located at the end of the dose knob is depressed resulting in the administration of the desired dose. U.S. Pat. No. 6,248,095 is incorporated herein by reference in its entirety.
Prior art medication delivery pens, however, suffer from the drawback that if the dose knob is adjusted beyond a desired dose (i.e., an error in dosing is made), a waste of time or medication results in correcting to the desired amount. In one manner of correcting for the mistake, the dose knob can be “dialed back” to the lower dose amount and there set. However, such “dialing back” will result in the wasteful expulsion of medicine commensurate to the amount corrected. For example, if the pen is “dialed back” from a 300 μl dosage to a 250 μl dosage, 50 μl will be wastefully expelled. Alternatively, some pens, such as that disclosed in U.S. Pat. No. 6,248,095, provide for a reset mechanism which allows for the dose knob to be disengaged and returned to a zero position without “dialing back”. Such reset typically involves “dialing out” the dose knob to its fullest extent where it is disengaged and then returning the dose knob back to a start position. Although it is possible to reset the pen, additional time and effort is required to do so.